An organic light-emitting device, such as an organic electroluminescent device (organic EL device), has been actively studied for enhancing the light emission efficiency thereof. In particular, various studies for enhancing the light emission efficiency have been made by newly developing and combining an electron transporting material, a hole transporting material, a light-emitting material, and the like constituting an organic electroluminescent device. There are studies focusing on a compound emitting delayed fluorescent light.
Delayed fluorescent light is fluorescent light emitted through such a mechanism that a compound in an excited state through application of energy undergoes reverse intersystem crossing from the excited triplet state to the excited singlet state, and then the excited singlet state returns to the ground state to emit the fluorescent light, and the delayed fluorescent light is fluorescent light that is observed with a delay from the fluorescent light directly emitted from the excited singlet state (normal fluorescent light). With the use of the compound capable of emitting delayed fluorescent light as a light-emitting material of an organic electroluminescent device, the energy of the excited triplet state, which has a large formation probability, can be converted to fluorescent light and thus can be effectively utilized for light emission, from which a high light emission efficiency can be expected. Accordingly, compounds emitting delayed fluorescent light have been actively developed, and there have been some proposals of the utilization of the compound as a light-emitting material.
For example, PTL 1 describes that a compound having a benzene ring having substituted thereon two cyano groups and one or more carbazolyl group or the like is a compound capable of emitting delayed fluorescent light. The literature describes that the use of the compound as a light-emitting material of an organic electroluminescent device and the like can enhance the light emission efficiency.